1. Field of the Invention
The present invention relates to a microchannel plate assembly which combines a microchannel plate and electrodes used for multiplying incident electrons in a charged particle detector and the like.
2. Related Background Art
Microchannel plates (hereinafter, referred to as “MCPs”) have been known as devices for multiplying and outputting incident electrons. A typical MCP structure is shown in FIG. 11. An MCP 6 is a thin disk-like structure made mainly of glass, in which arranged are a large number of small-diameter holes 62 passing therethrough in the thickness direction except for an annular peripheral portion 61, and formed at both surfaces are conductive films 63 by evaporation. As the material of the conductive films 63, INCONEL (registered trademark) from Special Metals Corporation can be used, for example. The conductive film 63 is formed, without covering the entire surface of the MCP 6, with the peripheral portion 61 of the MCP 6 exposed 0.5 mm to 1.0 mm from the peripheral end.
The MCP 6, as shown in FIG. 12, as a result of arranging an input-side electrode 4 and an output-side electrode 7 at the sides of front and back surfaces, respectively, and being applied with a predetermined voltage by a power supply 15, discharges secondary electrons when charged particles 16 such as electrons or ions made incident into the holes 62 collide with sidewalls of the holes 62, thereby multiplying and outputting the incident electrons.
Because MCPs are made mainly of glass and used by being supplied with a high voltage in high vacuum as such, handling thereof requires caution. Because there may be a case of replacement not only in manufacturing but also after being incorporated in apparatuses due to the end of life and the like, techniques for integrating MCPs with input-side and output-side electrodes to facilitate handling in manufacturing and replacement have been developed.
The techniques described in JP2005-351887A (hereinafter, referred to as “Patent Document 1”) and JP2007-87885A (hereinafter, referred to as “Patent Document 2”) are examples of such techniques, in which the MCPs and electrodes are stored together in an outer shell and fixed for integration. FIG. 13 and FIG. 14 show the construction of a detector cartridge, which is an MCP assembly described in Patent Document 1. The detector cartridge 60 is a substantially disk-like structure as shown in FIG. 13, and an internal construction thereof is as shown in FIG. 14. Concretely, the two MCPs 55 and 56 are stored in a case 58 while being sandwiched with an input-side electrode 54 and an output-side electrode 57. In this case, the MCPs 55 and 56 are arranged in an opening located in the center of an annular centering ring 65 so as to prevent the MCPs 55 and 56 from in-plane misalignment. On a front surface of the input-side electrode 54, an insulator 53 made of an insulating material, a wire mesh-like mesh 52 and a mesh electrode 51, and a ring retainer 50 are arranged, and the ring retainer 50 and a case 58 are screw-mounted together.